This invention relates to multifocal intraocular lenses. More particularly, the invention relates to multifocal intraocular lenses adapted for use in a phakic eye, that is in an eye which also includes the natural lens.
Intraocular lenses (IOLs) are commonly used to modify vision. For example, IOLs are used to replace the natural lens of the eye when warranted by medical conditions. A common practice is to implant an IOL in a region of the eye known as the capsular bag or posterior capsule after the natural lens has been removed.
IOLs may be implanted in regions of the eye other than in the capsular bag. For example, monofocal IOLs, that is IOLs which have a single vision correction power, have been implanted in the anterior chamber at the front of the eye, even with the crystalline natural lens remaining in place. In addition, monofocal IOLs have been implanted in the posterior chamber even with the natural crystalline lens being present. Such monofocal IOLs are designed to correct a single vision deficiency, for example, myopia, present in the eye.
Neilsen U.S. Pat. No. 5,158,572 discloses a multifocal intraocular lens useful primarily as a replacement for the natural lens, for example, after a lens extraction operation in which the natural lens is removed. This patent very briefly discloses that the intraocular lens can in some cases be used as an adjunct to the natural lens. However, this patent does not disclose any further special or even specific characteristics of a multifocal intraocular lens used in conjunction with a natural lens as opposed to such a multifocal lens used after natural lens extraction.
Over time, as a human ages, the normal human eye gradually loses the ability to accommodate, that is to focus on objects located at different distances from the eye. This loss of accommodation is generally identified as presbyopia. The natural lens may remain clear and otherwise functional in directing light to the retina of the eye. In this situation, spectacles are often used to correct the presbyopia. In addition, there are varying degrees of presbyopia that are, at least generally, related to the age of the human subject. For example, early stages of presbyopia may occur in individuals in their twenties, and residual accommodation of the natural lens may remain in individuals in their sixties, seventies and beyond. Many people wish to avoid wearing spectacles, particularly in their younger years, to maintain a youthful appearance.
It would be advantageous to provide an intraocular lens adapted for enhanced effectiveness in an eye including a natural lens.
Intraocular lenses (IOLs) for use in mammalian eyes having natural lenses have been discovered. Such IOLs are particularly useful in phakic eyes in which the natural lens has lost a degree of accommodation or accommodative ability, that is in a partially presbyopic eye. The present IOLs have multiple optic powers, that is are multifocal, preferably having an optic power for each object distance at which an object is formed on the retina. The multifocal design of the lens preferably is mechanically fixed so that the multiple optical powers can operate substantially simultaneously.
An important feature of the present IOLs is that they are configured to take into account the remaining accommodation ability or capability of the natural lens so that enhanced vision is obtained irrespective of the degree of presbyopia present. Put another way, the present IOLs are configured or customized to take into account the specific degree of presbyopia present in the eye in which the IOL is to be implanted. The present IOLs can be made using conventional materials of construction and conventional manufacturing techniques and can be implanted in the eye using procedures which are conventionally employed in implanting other monofocal or multifocal IOLs.
In one broad aspect of the present invention, IOLs are provided for use in mammalian eyes having natural lenses. Such IOLs comprise a lens body sized and adapted for placement in the eye and having a baseline optical power and at least one optical add power, preferably a plurality of different optical add powers. At least one of the optical add powers, preferably each of the add powers, is reduced compared to the baseline optical power of the lens body relative to the corresponding optical power of a similar intraocular lens adapted for placement in a similar eye in which the natural lens has been removed. Such reduced optical add power or powers provide only partial restoration of accommodation. In other words, the reduced optical power or powers of the IOL alone do not provide for full accommodation. However, the reduced optical power or powers of the present IOLs, when combined with the residual natural accommodative ability in the early or partial presbyopic phakic eye, provide enhanced vision, for example, enhanced near vision.
In another broad aspect of the present invention, IOLs are provided for use in mammalian eyes including natural lenses having accommodative capability. The IOLs comprise a lens body sized and adapted for placement in the mammalian eye and having a baseline optical power and at least one optical add power, preferably a plurality of different optical add powers. At least one of the optical add powers, preferably each of the optical add powers of the lens body has a magnitude so that the lens body when placed in the mammalian eye, in combination with the natural lens, provides enhanced vision. This enhanced vision continues as the accommodative capability of the natural lens in the eye decreases. Thus, the magnitude of the add power or powers of the lens body may provide only partial restoration of full accommodation in and of itself. However, when combined with the residual natural accommodative ability in the early presbyope, such IOL provides enhanced vision, for example, enhanced, or even substantially full, near vision or reading vision ability. Even after the early or partial presbyopic subject or presbyope progresses to full or absolute presbyopia, often after more than about five (5) or about ten (10) or about twenty (20) or more years, the reduced add power or powers of the present IOLs provide enhanced vision, for example, at intermediate distances.
The IOLs in accordance with the present invention preferably provide a range of optical powers to allow focusing of distance, intermediate and near images on the retina. In one very useful embodiment the IOL has a simultaneous vision design, that is a concentric and cylindrically symmetric series of zones, such as annular zones, of varying optical power which provide additional or add power for vision at other than distance.
The designed principal optical add power, in particular a near optical power, of the present IOLs preferably is less than the full optical power required for near reading in a pseudophakic subject, that is a subject not having a natural lens in place. This reduced power preferably is less than about 2.5 diopters in the spectacle plane. In a very useful embodiment, the designed principal optical add power of the IOL is reduced, which, in turn, reduces the effects of halos around lights at night while providing acceptable near and/or intermediate vision correction.
The present IOLs preferably provide continuous visual correction or enhancement from distance to near for early (or partial) presbyopes. However, late or absolute presbyopes gradually find a reduction in near vision capabilities employing the present IOLs. Thus, such late, or absolute, presbyopes may require additional vision, e.g., spectacle, assistance for specific near reading tasks. Regardless of the eventual loss of near vision, the additional optical power required for near work is less than that which would be required without the present IOLs. This reduced optical power requirement allows the use of bifocals or progressive spectacles which have fewer field distortions, image jumping and other deleterious visual effects.
The present IOLs may be placed at any position along the optical axis of the eye. For example, the present IOLs can be carried by or secured to the cornea of the eye, for example, such as a corneal implant, e.g., inlay or onlay. Also, the IOLs can be placed posterior of the posterior chamber. The present IOLs may further comprise a fixation member or members coupled to the lens body and adapted to facilitate fixating the IOL in the eye. The fixation member or members preferably are adapted to be placed in the anterior chamber of a mammalian eye or in the posterior chamber of a mammalian eye.
The more likely locations for the present IOLs are in the anterior chamber, for example, with a fixation member or members in the angle of the eye; in the anterior chamber, for example, with a fixation member or members located in contact with the peripheral iris; in the anterior chamber with a fixation member or members located through the iris into the posterior chamber and in contact with the sulcus; or the posterior chamber between the iris and the natural lens with a fixation member or members in contact with the sulcus.
The design of the present IOLS preferably provides that the lens body include a plurality of different regions each having an optical power, for example, a different optical power. The lens body may include a plurality of annular regions each having an optical power and extending radially outwardly from the central axis of the lens body. The lens body preferably is generally circular around the optical axis of the lens body, although other configurations and shapes may be employed and are within the scope of the present invention.
The lens body preferably is configured so that at least one of the optical add powers is reduced by at least about 10%, and more preferably at least about 20% (in terms of diopters from a baseline distance correction optical power) relative to the corresponding optical power of the similar IOL adapted for placement in a similar eye in which a natural lens has been removed. Still more preferably, each of the add powers in the lens body is reduced by at least about 10% and even more preferably at least about 20%, relative to the corresponding optical power of the similar IOL adapted for placement in a similar eye in which the natural lens has been removed.
The present lens bodies preferably are deformable for insertion through a small incision into the mammalian eye. The lens bodies preferably comprise a polymeric material.
In another broad aspect of the present invention, methods for treating presbyopia in a mammalian eye including a natural lens are provided. Such methods provide for placing in the mammalian eye an IOL including a lens body having a baseline optical power and at least one optical add power, preferably, a plurality of different optical add powers, so that the lens body, in cooperation or combination with the natural lens, provides enhanced vision. Intraocular lenses as described herein may be employed in the present methods. The enhanced vision provided by such methods preferably is relative to the vision provided by the mammalian eye without the intraocular lens. The enhanced vision provided preferably is enhanced near vision, particularly in early or partial presbyopes. As noted above, as the subject progresses to full or absolute presbyopia, the enhanced vision provided by the present methods preferably is enhanced intermediate vision.
Each and every feature described herein, and each and every combination of two or more of such features, is included within the scope of the present invention provided that the features included in such a combination are not mutually inconsistent.
These and other aspects of the present invention are apparent in the following detained description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals.